Multiplex signaling system



A. N. GOLDSMITH MULTIPLEX SIGNALING SYSTEM May 5,1942.

.Filed Sept. 1,1959 4 Sheets-Sheet l T* my.

V+ Y ww l INVENTOR. v y N. GOLDSM/TH ATTORNEY.

May 5, 1942- A.- N, GoLDsMlT-H MULTIPLEX SIGNALING S'YSTEM 4Sheets-Sheet 2 Filed Sept. l, 1939 INVENTRA ALFREDN. GOLDSM/TH ATTORNEYPatented May 5,1942

UNITI-:nv STATES PATENT OFFICE gmane mm SIGNLING SYSTEM Alfredv N.sendmail, New to Radio Corporation of Delaware tion oi' geen, N. r.,einer i www# =8Clalms.

My present invention relates to signaling systems of the multiplex type,and more particularly theinvention relates to a method of' multiphasetime division in transmission and recep tion which is dependent on theselection of sections of a. saw-tooth timing wave.

One of the primary objects Vof my invention is to pick-up sound from aplurality of spaced sources; to transmit the electrical version of thepicked-up sound by a recurrent, or cyclic time-division of thetransmission channel; and to reproduce the picked-up sound with areasonably close approximation to the spacial differences and effects ofthe original sounds.

Another important object of my invention is to provide a generallyuseful method of multi-phase time division in transmission and receptionwhich is dependent on the selection of sections of a recurrent saw-toothtiming wave for the first function required for time division, and tocomplete the time division by a system of progressive cut-offs ofearlier-phased portions of the respectively-or preferentially from thelocations A-B-C. It can, also, be assumed that' points A-B-C representsuccessive locations of one or more moving persons. The purpose of theinvention, is to transmit electrical versions of the sound waves frompoints A--B-C inaccurate space relation so that the listener, at aremote` point, has conveyed to him the illusion of sterosonicreproduction.

The audio frequency output of each microphone may be passed through alow-pass filter when, as in this illustration, it is desired to limitthe audio range to be transmitted. Thus, filters multiphase or multiplextransmission by means by reference to the following description taken inconnection with the drawings in which I have indicated diagrammaticallya circuit organization whereby my invention may be carried into effect.

In the drawings- Fig. 1 shows the transmitter end Vof a system embodyingmy invention,

Fig. 2 illustrates the receiver end of the system,

Figs. 3A to 3Q graphically show the operation of the various networks ofthe system of Figs. 1 and 2. e

Referring now Ato the accompanying drawings, and specifically to thetransmitting end of the system shown schematically in Fig. 1, numeralsI, 2 and 3 designate ,signal pickL-up devices. Three such devices aretaken illustrativelv, but two'or any greater number may be used. Whilemy invention is not 'restricted to the' specific case wherein thepick-up devices -are microphones, yet such illustration will be used toexplain the invention. Assuming that numeral 4' denotes a stage, orplatform, upon'which several persons are located at. positionsA---lBI--CI microphones I, 2 and 3 are positioned so as to pick-upsounds 1, 8 and'Qare interposed inthe lines leading from microphones I,2 and 3 respectively. Each filter has a cut-off at 10,000 cycles, forexample. Thoseskilled in the art are fully aware of the manner ofconstructing such low-pass filters. 'I'he filteredaudio energy isamplified, and audio ampli- 1fiers I4, I5T and I6 are associated withthe output of each of lters 1, 8 and 9 respectively.. Each of amplifiersI4, I5 and I6 may be any well known type of amplifier of audio energy.The amplied output of each amplifier, after suitable timed modification,is eventually :Impressed upon a mixing amplifier 39.

Lead 2l transmits the output of amplifier I6 directly to the mixingamplifier 39. However, the output of each ofl amplifiers I5 and Il isimpressed on amplifiers 35 and 36 respectively. Each of amplifiers. 35and 36 is of the so-called cut-off type. That is to say, each of theamplifiers 35 and 36 will be o'f the type wherein application ofexcessive, or additional, negativenbias to the signal grid, or anyauxiliary grid, will result in cutting off transmission through the tubeand amplifier. Such ampliers are wellv known, and need not bev describedin more detail beyond stating that the time constant or speed ofoperation of the biasing means for cutoff in suchampliflers must bechosen so that the cut-off will accurately follow at the highest ratethe actuating potentials hereinafter de-v scribedl The output ofamplifier as is impressed y by rendering;A it operative.

the oscillator is well above audlbility. Frei quencies in the range from15,000 cycles to about 100,000 cycles or more may be employed. For

the purpose of illustration let it be assumed thatA the oscillatorfrequency is 100,000 cycles.. The oscillator should have asy gradual andlinear a rise in its wave form, anad as abrupt a fall in the latter, asis obtainable. In general, saw tooth oscillators are conventional andwell own, particularly in television, and those skilled in the artshould readily vbe able to construct suchate-phase amplifier, isdesigned to operate only.

when anything more than a small positive voltage is applied throughconnection 2t. A bias source 23 is inserted in connection 3E betweenvoscillator 20 and the signal input, or other control, electrode ofamplifier l5, to apply to ,the input electrode a negative bias whichisapproxi- .mately one-third the peak 'voltage/ of oscillator 20.

amplified rectified voltage output of network 30 may be applied to thesignal grid of amplifler 36 in order to vbias the ampliiler to cut-off.Of course, any other well known method of utilizing the voltage outputof network 30 may be employed for biasing amplifier 36 to cut-off. Aportion of the output of ampliler I6 is applied through lead 28 to thefull wave rectifier-amplifier network 3| The amplified, full-waverectified audio energy output of network 3| is applied to the amplifier35 in a sense to cut off the latter. Furthermore, the output of network3| is applied over lead 33 Hence, during the latter two-thirm of therising linear portion of the saw tooth wave a positive potential will beapplied to amplifier I5 there- In other words, bias source 23 biasesamplifier IE to cut-0E in the labsence of oscillations whose amplitudeexceed the predetermined value of negative bias. The bias source 2t isinserted in connection 22 so as to provide a negative cut-oil' bias foramplifier I8. 'Ihe latest-phase amplifier I8 is arranged so that itoperates only when anything more than a small positive potential isapplied through connection 22. The bias source 24 applies a. cut-oilbias to'. the input electrode of amplifier J6 for oscillator voltage upto approximately two-thirds the peak voltage of oscillator 20. Duringthe latter one-third of the rising linear portion ofthe saw tooth wave apositive potential is applied to` amplifier II therebyrenderin'g itoperative. Now. if the outputsof amplifiers Il and I5 were permitted tobe directly applied to the mixing ampliiler, equal time division betweenthe three phases of the saw tooth wave would not be secured. Thisfollows from the following consideration. v

It will beclear that earliest-phase output of amplifier I4 would existcontinuously. The intermediate-phase output of amplifier I5 would existduring the latter two-thirds of each transmission, or time-division,cycle. The latestphase outputof amplifier I6 would exist only during thelast one-thirdof such transmission cycle. In order to secure the desiredequal time division between the three phases networks 30 and 3| areprovided, and each network comprises a full wave rectifier followed byan amplifier. Amplified audio energy from amplifier I5 is impressed uponnetwork 30 through lead 29. The

audio energy impressed on network 30 is fullwave rectified; the derivedrectified audio energy is amplified, and then impressed on amplifier 36in a sense to cut oil.' the latter.v As explained previously amplier 3Bmay be of the usual -audio amplifier type but with appropriate frequencycharacteristic. and speed of cut-oil', and the to provide an auxiliarycut-oil bias for amplifier 33.

When there is anyl appreciable output from amplifier i6 there can be nooutput from amplflers 35 and 33, because the output of network 3|biasesamplifiers 35 and 36 to cut-off. Furthermore, when there is anyappreciable output from ampliier i5, there can be no output from amplier36 by virtue of the fact that network 30 biases amplier 36 to cut-off.Hence, through the action of networks 3E--30-35-3I the earliestphaseoutput occurs only during substantially the rst third of thetransmission cycle; the intermediate-phase output occurs substantiallyonly during the second third of the transmission cycle; and thelatestphase`output occurs only duringl substantially. the last third ofthe transmission cycle. lt should be here emphasized that the presentmethod of producing equal time division is purely illustrative. 'Forexample, the bias source 23 may control network 30 directly. Further,bias source 24 may control the network 3i directly. In general, theequal time division arrangement utilizes later-phases of transmissionresulting from a cycle of transmitting-time division to cut oliearlier-phases.

In addition to the time-divided outputs of the microphones, there is fedto the mixing amplifier 39 any form of synchronizing, controlling ortriggering signal. For example, an impulse generator- 4I, operating at33,333 cycles or impulses per second, may have its output impressed onthe mixing amplifier 39 by lead 43.

The impulses from generator 4I .are directly used to modulate thetransmitter through lead 40. The duration of these impulses, as added tothe modulation, is very brief, as for example 3&00000 or $600000 second.In general, the duration ofeach impulse should be brief in comparisonwith the time between impulses so as not to interfere with theearliest-phase transmission, as will appear hereafter. Hence, at thereceiver they can be separated out from the complex modulation Wave by afrequency-selective method.4 This has the advantage of simplicity and ofpermitting modulation of the transmitter. The lead 40 will transmit tothe subsequent transmitter equipment a. composite wave delivered byamplifiers 36, 35, I6, as well as the impulse generator energy. 'Ihefunction of the` impulse generator Il is to control theoscillationsproduced by the saw tooth oscillator 20 so that proper timedivision of each audio wave is secured. This is .accomplished by feedinga portion of the output -of generator 4I through lead l2 to theoscillator 20, which is thus triggered and accurately timecontrolled.Such saw tooth oscillators, e. gi, of

gaseoso over a radio frequency distribution line if desired.

At the receiving terminal of thesystem the modulated waves may besubjected to usual and well known steps to derive the modulation fromthe carrier. The receiving network may be of any well known type, itbeing understood that the final demodulator (not shown) of the networkwill deliver to the line I the composite modulation wave. A low passfilter 55, having a cut-off .illustratively at about 150k. c., transmitsto amplifier 59 the composite modulated 100 k. c. wave cordingly,forming in their totality a composite modulated 100 kf c. wave. I'hefilter 54 is a high pass filter, and passes the impulse energy of 200 k.c. or above. The Vfilters 5d and 55 may be of any Well known type, andthose skilled in the art are fully aware of the' manner of designingfilters l of these types.

The 200,000 or-higher cycle impulses are separated out from thecomposite modulation wave (Fig. 3K) .by selector ilters 54 and 55. Themethod employed may follow that shown on page 1289 (Figs. 11-13) of're1evlsion," ltoi. 1,1Ju1y 1936 (published by RCA Institutes, TechnicalPress, New York city). The latter is merely a modifiedfrequency-selective method. The'spccinc values given herein for thesynchronizing impulses andsaw tooth oscillatorare purely illustrative.The greater the difference between the length of a section of thecomposite audio Wave RC (Fig. 3M) on the one hand, vand the shorter thelength of the synchronizing impulses TA or RA (Figs. 3D and 3L) on theother hand, the

- easier will be theeffective and economical separation of these twocomponents of thewave' modulation at the networks 5 and 55 ofthereceiver.

The impulse modulation energy is amplified as required by amplifier 5B.'Ihe impulses are applied to controllable saw tooth oscillator 63 so asto control the latter in the same manner asdetooth oscillator 63 isconstructed as nearly as is possible to be identical in operation withoscillator in frequency, phase, slopes, and linearity of rising andfalling portions of its generated wave. The output of oscillator 63 isimpressed on amplifiers 1I, 12, 13 by connections 64, 65 and '86respectively. Amplifier 1| is constructed and arranged to' be activewhenever there is any potential of positive polarity applied to' itssignal grid. If desired, connection 64 may be omitted,

a small constant positive activating potential be- .,ing' thencontinuously applied to amplifier 1|.

loudspeakers of any desired type. They are similar to platform d of Fig.1, and the speakers can be arranged to correspond to points lLl--B-C.The soundwaves issuing from the loudspeakers are desired to be in thesamephase and wave-form relationship as the sound waves at themicrophones. The circuit now to be decomposite wave RC of Fig. 3M intothe wave patterns lat Figs. 3H-3I-3J..

This is necessary in order to separate and select the individual channelsignals which are derived from thev multiplex reception, all in the vfashion also decribed in connection with a later description herein ofFigs. 3A to 3Q. The saw scribed provides the means -for "analysis of thee The bias source B1 is included in connection 65, and applies a.negative voltage to the signal grid of amplifier 12, and the value ofthe negative bias'isequal to one-third of the peak voltage of oscillator53. Hence, the amplifier 12 is operative during the latter two-thirds ofeach transmission cycle as defined above. The bias source 6d is includedin connection 66; the bias magni- 'tude is equal to two-thirds of thepeak voltage of oscillator 53. .Amplifier 13 will then be oper-V ativeduring the last third of each transmission cycle. The three amplifiers1i, 12, 13 have similar characteristics, and function in the manner ofcontrolled amplifiers Il, I5 and I6 of Fig. l.

A portion of the output energy of amplifier 13 is applied to the network88. The latter is a full wave rectifier and amplifier ofthe typedescribed in connection with Fig. 1. The output of network 88, which isamplified full wave-rectified voltage, is applied as grid ybias to apair of cutoff amplifiers 81 and 85. Lead 83 applies the cut-oil bias toamplifier 81, while lead 82 applies the cut-oil bias to amplifier 85.Each of the cut-oil ampliers 81 and 85 is designed so that transmissionof energy therethrough is prevented when a small biasing voltage isapplied over leads v82 and 83. The output of cut-off amplifier 811sapplied to lamplifier 12 by lead 8l, while lead 8U feeds the output ofamplifier 85 to a control element of amplifier 1i. The full waverectifier-amplifier network 86 rectiiles a portion of the voltage oftherampliiler 12; the amplified rectified voltage is applied over lead,8l to a control element of cut-off amplifier 85.

4description of Figs. 3F, 3G, 3P and 3Q. lDuring the' active periods ofthe controlling waves represented in these figures they must ,cause thecut-oil' ofv all earlier waves, and the important point is that theymust do this irrespective of their polarity. That' is; the negativepolarity variations of wave, TG, for example, (Fig. 3F) must be aseffective in producing cut-off as are 'thosevariations which are ofpositive polarity. vFor this reason full wave rectification is 1em-Figs. 3A to 3Q inclusive serve to render the Jfunction of thetransmitter and receiver networks more clearly understood. It is to beunderstood that the various curves shown in these figures are plottedon'the same scale, and for that reason the curves are to beunderstood asif plotted with the same ordinates and abscissae upon one curve sheet.Each of the curvesA has associated with it the letter T to designatethat the curve pattern exists at the transmitter, and the letter R todesignate that the curve pattern exists at the receiver. Furthermore,each of the curves has associated with it numerals corresponding tosimilar numerals designating; conductors in Figs. 1 and 2xso that it can:readily be determined at which portion of the systems shown in Figs. 1and 2 the particular wave patterns shown in Figs. 3A-3Q exist. It will,also, be noted that certain of the wave patterns are duplicated in thetransmitting and receiving systems. Hence, by following through Figs. 3A

to 3Q inclusive, it is possible to have a clear picture of the manner inwhich the various networks of the system function to change the natureof the waves transmitted therethrough.

Figs. 3A, 3B and 3C show respectively small sections of an audio waveimpressed on microphones I, 2 and 3 respectively and passing throughpanded horizontal time scale. It will be understood that the threecurves TC, TD and TE are leads 4, 5- and 6, and necessarily on a muchexsimultaneous representations of sections of audio' form of the sawtooth oscillator 2l, and it willA be noted that eachsaw tooth cycle hasa duration of the group or cycle A, B, C. Additionally, the letters TAdenote the `synchronizing impulses having a duration of about '1/2oo,ooosecond. The impulse generator 4I, as those skilled in the art are fullyaware, is constructed` to produce impulses having a duration of l/maooosecond, or less, and spaced apart .a period of time equal to the periodA, B, C which is taken as ham second.

Fig. 3D, furthermore, shows the fact that the saw \toothoscil1ationimpulses are transmitted over leads I1, 2I and 22, but that theoscillator is operative over lead I1 throughout its entire cycle,whereas it is operative for only 3; loflits cycle over lead I8', and itis operative for only M; cycle over lead I3. The eiect of the saw toothoscillator, and biasing networks 23 and 24, on the wave forms TC, TDandl TE is shown in Figs. 3E, 3F and 3G.

Fig. 3E shows curve TF substantially corresponding to that of curve TC,and indicates that TF is the wave form .atlead 25. This is true sincethe saw tooth oscillations are constantly latter the modulated carrieris selected, amplified line wave form TJ exists. In this way, the cutoffampliers are operated by the networks ll and 3| regardless vofthe'polarityof the energy passing through to the rectier networks. The

reason for full wave rectification, with resulting cut-oi! actionregardless of the`polarity of thecontrolling wave as desired, thusbecomes clear.

Figs. 3H, 3I and 3J show the wave forms TK,

'I'L and TM respectively which exist at leads 31,

38 and 21 respectively. In other words, Fig. 3H shows the manner inwhich the curve TF of F18. 3E has been chopped up by the action ofnetworks 30 and 3|. On the other hand, Fig. 3I shows how curve TG ofFig. 3F hasl been further chopped up or divided into phased sections bythe action oi network 3l. It will. now be seen that the threeoriginalaudi wave forms have been chopped up according to the timedivisions A, B and C, but

that each of curves" TK, TL and TM represents course, the completemodulated carrier wave requires the combination of TN with its mirrorimage, to form the envelope curve of the modulated radio frequencycarrier in the transmitter, in order to get an accurate picture of themodulated carrier wave. The complex wave form TN,

then, is transmitted to the receiver point. At the and demodulated inthe usual manner.` For example, the4 stages prior to lead 5I in Fig.2'may y exists.

Fig. 3L shows the synchronizing impulse curve form RA which is found atlead 58 at the output 28. It will be seen that this wave-form is due tothe fact that the saw tooth oscillator is only operative during the lastV3 of each'saw toothl 'wave cycle A, B,-C. -In Fig. 3F the dotted curveslTI denote the eiect of thefull wave rectication,

and the additional fact that at lead Il the wave form has the shape ofthe dotted curves. In Fig. 3Q it is shown that at leads 32 and 33 thedotted of highv pass (impulse selector) lter 5l.' Comparison of thiscurve with Fig. 3D shows that the synchronizing impulses are recoveredin accurate relation relative to the periodsv A, B, C. From Fig. 3M itis seen that the wave form at lead l1, as well as at leads GII, 6I,02,'is represented by the curve RC. -In other words', the low passfilter |55 passes the composite of curves TK, TL, TM,

but without including the synchronizing impulses. lThe problem now is toanalyze the wave form RC into the component forms RI, RJ and RK of Figs.3H, 3I, 3J respectively. From the latter figures it will be seen thatthese component wave .forms exist at leads 1I, 15 and 1S respectively.When the reproducers 11, 18 and 19 are respectively actuated by theimpulses RI, RJ, RK, there will result the audio wave forms RL, RM andRN respectively. These, it will be recognized, are the original audiowave forms of Figs. 3A, 3B and 3C.

analysis of curve form RC is accomplished by producing saw toothoscillations RB (Fig. 3D) which correspond to those produced at 2l inrFig. l. The synchronizing impulses RA (Fig. 3L) maintainthe wave formsRB and TB in accurate synchronism. This is done bylapplying the impulsesat 58 to the oscillator Il.' The saw tooth oscillations are effectivecontinuously Fig. 3D; .it is, also, shown that the absence of a biasingmeans in lead'E permits continuous eii'ect of the oscillations. It willbe noted that this is the same type of control effected in Fig. 1.

Considering, now, Fig. 3N it will be readily appreciated that curve RDwill be secured at the output of ampiiiier 1l if the cut-ofi voltagefrom amplier 85, and which voltage is fed over lead 80, is absent. Thiscurve RD is similar to curve RC of Fig. 3M, However, at the outputamplier 12, and without considering the action of the cut-off voltagefed over lead 8l, the wave form is that of the full line curve RE ofFig. 3P. Due to the action of the oscillator voltage ied over lead 69,and which is only effective during two-thirds of the cycle, the A"period has been chopped out. Similarly, at the output oi ampliiier 1S,and at lead 89, the wave form is as shown by the full line curve RF inFig. 3Q.k Due to the one-third eiectiveness of the oscillator voltage atlead 10, the A and "B sections of the curve RC have been chopped out.

The action of the fullwave rectifier-amplier 86 on the curveshape RE isshown by the l dotted line curve RG in Fig. 3P. Again, the

full Wave rectiiication action of network 88 on curve form'RF is shownby the dotted line curve RH in Fig. 3Q. In other words, the curve RG isthe wave form at; lead 84, and the curve RH illustrates the Wave form atleads 82 and 83. The cut-0E bias fed over lead 82 causes amplier 1l'tobe inoperative during each C period; the cut-,ou bias fed over lead 83causes amplifier 12 to be inoperative during each C period. Furthermore,the cut-oi bias fed over lead 811 causes amplier 1l to be inoperativeover each B period. Thetotal result is,then,

that at the output lead 14, 15 and 16, the curve forms are RI, RJ and RK(Figs. 8H, 3I,`3J) respectively.

Itwill now be seen that the audio waves produced at reproducers 11, 18and 19 are not ,only of the same form as the waves impressed atmicrophones l, 2 and 3, but they have the same relative phaserelationship. Hence,.at the reproducers `there is created a sterosonicillusion. It may be added that, if delays inthe control circuits ofFigs. 1 and 2 have an appreciable effect, they can be' equalized andcompensated as desired by the insertion of Well known non-frequencyselective delay networks in one or more of the elements 42, 43, l1, 2|,22, 28, 33, 32, 29, 5S', 64, ,85, 6B, 89, 92, 86, 80 or the like. Theterm non-re-entrant wave? used in the claims means a Wave which, foreach cycle, cannot be cut by va horizontal line (parallel b to the zeroaxis of abscissae) in more than two points of the waveoutline.

Detailed analysis of the time selection produced by the system .asdescribed herein ndicates that during portion B of the saw tooth wavecycle, and during the brief and rapidly falling portion thereof, -it ispossible for a short section or burst of energy to -pass' throughconductor 38 to mixing amplier 39 in Fig, 1, the amplitude of this briefsection being pro- Wave generated from 2 and I5. Inasmuch as such a`brief section of electrical energy might sufliciently resemble one ofthev impluses conportional tothe momentary amplitudeof the tributed tomixing amplier 38 by impulse generator 4I, thus disturbingv thesynchronizing means used in the system as disclosed, any one of thefollowing means may be used to' eliminate this generally unimportanteiect.v As a first:

means, there may be inserted in conductor 38 a lowpass filter with a.cut-of! of approximate- 1y 150,000 cycles per Second. Thus briefsections of electrical energy are prevented from passing through 38 ltolamplifier 39. Alternatively, cutoff amplifier 3B may be designed toaroplifyfrequencies up to say 150,000 cycles but not beyond, thuspreventing any brieier sections of electrical energy from passingtherethrough.

While I have indicated and described a system ,for carrying my inventioninto enact, it

will be apparent to one skilled in the art that my invention is by nomeans limited to the particular organization shown and described, butthat; many modications may be' made without departing from the scope oi'my invention, as set forth .in the appended claims.

1. In combination with a plurality oi' audio signal transmissionchannels, the signals ci the channels being'different, a saw toothoscillator,

separate connections from said oscillator to said Y channels forcontrolling signal transmission therethrough, a timing impulsegenerator, means responsive to'said impulse generator for controllingsaid oscillator, means vin circuit with the oscillator and at least oneof the channels for preventing transmission through the one channelduring transmission through the remaining channels, and additional meansresponsive to signals in said one channel for preventing transmissionthrough the remaining channels during periods oftransmission through theone chann' 2. In combination, vmeans for the production of amultiplicity of intelligence-carrying signals,

means for initiating cycles of successively selected 'time sectionsrespectively of each of said signals, such c yclic groups of timesections being Y each brief in comparison with the shortest half- Wavecycle of any of thesaidsignals, a timing impulse Agenerator forproducing cyclically-repeated, variable amplitude impulses with eachimpulsebrief in duration in comparison with each of the selectedl timesections, means responsive to said impulses for initiating operation oisaid time section selection means, and means :for simultaneouslytransmitting the cyclically repeated initiating impulses and the cycleso! time sections oi 'each of the said signals in superimposed relation.

3. In combination with means for producing and transmitting a compositesignal composed of cycles of successively selected time sectionsrespectively of a multiplicity of intelligence-carrying signals whereinthe cyclic groups of sections are brief in comparison with the shortesthalf-wave cycle of any of said signals and superimposed cyclicallyrepeated impulses which are brief in comparison with each of the saidselected time sections, means for receiving said composite signal, meansresponsive to the frequency and wave shape of said impulses forseparating the impulsive componentsof the received com'- posite signal,means initiated by the separated impulses for selecting individuallycorresponding time sections of each of the intelligence-carryingsignals, and means for individually reproducing each such selectedsignal from such selected time sections of each individual signal.' .y

4. In a system of multiplex communication, the method which includesgenerating a composite signal including oyclically recurrent and timedsections of each of va multiplicity of :lntelligence-carrying signals.such cyclic groups of sections being brie! in duration compared with theshortest lhalf-wave cycle of any of the said signals, and concurrentlysuperimposing on said timed sections impulsive signals for theinitiation and timing of each oi such above mentioned cyclic groups oisections, such impulsive signals being brief in comparison with theshortest of,

the timed sections o! any of the intelligencel carrying signals. i

5. In combination with means for producing a plurality oi.' independentaudio signals, means for 'initiating cycles of successively selectedtime sections respectively of each oi said signals. said. cyclic groupsof time sections being each brief in comparison with the shortesthalf-wave cycle of of said audio signals, means i'or providimpulses-brief in duration in comparison with each o! the selected timesections, means utilizing said impulses for eiecting operation of saidtime section selection means for each selection cycle. and means forsimultaneously transmitting the cyclicauy repeated initiating impulsesand the cycles oi time sections of 'each ofthe audio signals insuperimposed relation.

6. In combination with means for producing a plurality oi! independentaudio signals', means i'or initiating cycles oi' successively selectedtime Vsections respectively oi each of said signals, said aasaosc naisin superimposed relation, means for re ceiving said simultaneouslytransmitted impulses and time sections at a4 point remote from the.1

signalproducing means', means initiatedby the impulsive components otthe received signals for selecting individually corresponding timesections oi each audio signal, and means for individually reproducingeach such selected signal from such selected time sections.

7. InV combination with a plurality of audio signal transmissionchannels. the'signals oi the channels being of diiIerent wave form;means for producing a control wave of predetermined shape, connectionsbetween said means and channels for lapplying said wave to said channelsfor controlling signal transmission therethrough in a predeterminedcyclic sequence, Y -means in circuit .with the said means and'at leastone of the channels i'or preventing transmission through the one channelduring trans'- mission through the remaining channels, and additionalmeans. responsive to signals in said -one channel for preventingtransmission through l the remaining channels during periods of trans?mission through the one channel.

8. Incombination with a plurality of signal transmission channels, thesignals of the channels being of dinerent wave form, a saw-toothoscillator forl producing a control wave, connections between theoscillator/and channels for applying said control wave to the channelsfor controlling signal transmission in a lpredetercyclic groups oi timesections being each brief in comparison with the shortest haii-wavecycle mined cyclic sequence, means for producing timing impulses, meansresponsive to said timing impulses toi-.controlling the oscillator,means rer sponsive. to the oscillator control wave for prel `oi!transmission venting transmission through ,one channel duringtransmissionthrough the remaining channels, and additional meansresponsive to signals in said one channel for preventing transmissionthrough the rem thro h said one channel,

ALFRED N. GOLDSMITH.

' channels during periods

